Tetsuyasu Hirata

Serovirological Study of Vestibular Neuronitis

A serovirological study to clarify the pathogenesis of vestibular neuronitis was made on 44 patients. The diagnosis of vestibular neuronitis was made under the diagnostic criteria. Sera from all 44 cases were collected twice or more at defined intervals. Of these, 36 cases were treated as paired sera. Seventeen out of 36 paired cases showed significant change in serum viral antibody titer (HSV, 2 cases; CMV, 1 case; EBV, 7 cases; rubella, 2 cases; adeno., 2 cases; influ. A, 1 case; influ. B, 2 cases). It was assumed that infection caused by these detected viruses played an important role in the onset of vertigo in each case.

Serum Viral Antibody Titer in Vestibular Neuronitis

Fifty-seven cases of vestibular neuronitis were evaluated for viral infection by means of serum antibody titer. The viruses tested were herpes simplex virus, varicella-zoster virus, cytomegalovirus, EB virus, adenovirus, influenza virus A, influenza virus B, parainfluenza virus 3, mumps virus, rubella virus and measles virus. Paired sera were examined in 49 cases among 57 cases, 26 cases showed significant change (four-fold or greater change) in viral antibody titer. Only one case (53-year old female) showed high HSV 1 IgM antibody level by ELISA method, so the vestibular neuronitis in this case was assumed to have a close relation to viral infection.

Detection of HSV—I Nucleic Acids in Rat Vestibular Ganglia

Rats were infected with HSV-I through the middle ear. DNA and RNA were extracted from the vestibular ganglia, trigeminal ganglia, cerebrum, cerebellum and brainstem in the productive or latent state after inoculation. DNA and RNA were applied for polymerase chain reaction (PCR) to detect HSV-I genomes. In particular, in the RNA PCR, the latent-associated transcript (LAT) mRNA, which is said to be present in the cervical or trigeminal ganglia at much lower levels during the productive state, was detected. In the productive state, DNA was clearly detected in all samples whereas LAT was detected only in the trigeminal ganglion on the inoculated side, cerebrum and cerebellum. In the latent state, DNA was detected in the vestibular ganglion only on the inoculated side, bilateral trigeminal ganglia, cerebrum, cerebellum and brainstem; LAT was detected in the vestibular ganglion on the inoculated side, the bilateral trigeminal ganglia and brainstem. These data indicate that HSV-I can establish latent infection in the vestibular ganglia in a similar way as in the cervical or trigeminai ganglia.

Compensatory process of vestibular neuronitis : from findings of combined galvanic test and caloric test

The compensatory process of vestibular neuronitis in 7 patients was followed up and evaluated using the Combined Galvanic Test (CGT) and other neuro-otological data. CGT is the simultaneous recording of both galvanic eye movement (GEM) and galvanic body sway (GBS), and has proved to be reliable in the diagnosis of retrolabyrinthine disorders. The results were as follows: The subjective symptoms remained in 3 cases from 1 month to 1 year. The recovery of the GBS response was seen earlier than that of both GEM and caloric responses. The recovery of GEM and caloric responses was observed at almost the same time. We observed the favorable recovery process of caloric response and GEM response in some cases which had recovery of GBS response within 4 weeks and suggest that the system of GBS response is different from that of GEM and caloric response. However, the systems of the latter two may be the same. We assume that the recovery of GBS response is earlier than that of GEM and caloric responses because the otolithic system recovers more easily than the semicircular canal system. The CGT and caloric test were reliable in examining the compensatory process of vestibular neuronitis.